Field of the Invention
The present invention relates to a method for producing a wet rubber masterbatch yielded using at least a filler, a dispersing solvent and a rubber latex solution as raw materials.
Description of the Related Art
In the rubber industry, it has been hitherto known that at the time of producing a rubber composition containing a filler such as a carbon black, a wet rubber masterbatch is used to improve the composition in workability and filler-dispersing performance. This masterbatch-used process is a process of mixing a filler and a dispersing solvent beforehand with each other at a predetermined ratio, and dispersing the filler into the dispersing solvent by mechanical force to prepare a filler-containing slurry solution; mixing the slurry solution with a rubber latex solution in a liquid phase; adding thereto a solidifier such as an acid to yield a solidified product; and then collecting and drying the solidified product. The use of the wet rubber masterbatch can give a rubber composition better in filler-dispersing performance and rubber properties such as workability and reinforceability than the use of a dry rubber masterbatch yielded by mixing a filler with a rubber in a solid phase. The use of such a rubber composition as a raw material makes it possible to produce, for example, a pneumatic tire decreased in rolling resistance and excellent in fatigue resistance, or such a rubber product.
The filler to be used is appropriately selected in a scope from large-particle-diameter fillers to small-particle-diameter fillers in accordance with the usage of the rubber product. In the case of using, for example, a small-particle-diameter carbon black species, the resultant vulcanized rubber is improved in, e.g., strength and abrasion resistance. However, particles of the small-particle-diameter carbon black species easily aggregate in the rubber composition, which is a raw material of the resultant vulcanized rubber, so that this rubber tends to be deteriorated in fatigue resistance.
Patent Documents 1 to 3 listed below each describe a wet rubber masterbatch into which a small-particle-diameter carbon black species is blended. However, it has been made evident that these masterbatches have a room for a further improvement from the viewpoint of an improvement of the resultant vulcanized rubbers in fatigue resistance.